<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>发布订阅模式</title>
  </head>

  <body>
    <script>
      // 时间触发器
      class EventEmitter {
        constructor() {
          // { 'click': [fn1,fn2], 'change': [fn] }
          this.subs = Object.create(null);
          // this.subs = {}
        }
        // 注册事件
        $on(eventType, handler) {
          this.subs[eventType] = this.subs[eventType] || [];
          this.subs[eventType].push(handler);
        }
        // 触发事件
        $emit(eventType) {
          if (this.subs[eventType]) {
            this.subs[eventType].forEach((handler) => {
              handler();
            });
          }
        }
      }

      // 测试
      let em = new EventEmitter();
      em.$on('click1', () => {
        console.log('click1');
      });
      em.$on('click2', () => {
        console.log('click2');
      });
      em.$emit('click1');
      em.$emit('click2');
    </script>
  </body>
</html>
